In what sense did the Roman Empire survive until 1453? is Rome still a power today?
That is a great question. Under the emperor Constantine, the Roman empire split into the east and the west. The west had several imperial cities, but the main city was Rome. In the east, the main city was Constantinople.
After Constantinte, more and more resources was put into Constantinople and therefore the city gained in power. For instance, the Roman law codes were made here under Justinian.
Eventually the West became weaker and weaker until the Germanic invasions. In 410, Rome was even sacked. In time, the Western empire was no more, but this was not the case in the east. The east continued to thrive, until the the Ottoman Turks sacked it.
Many people do not study the eastern empire, which is a shame. I'm glad that you are thinking about this. I should say that the west spoke Latin, but the east was Greek speaking.
Finally, let me answer your last question. Rome is not in power today. After the fall of the east, Rome ceased to exist. This should not surprise us, since kingdoms rise and fall all the time.